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Don't walk into Certainty::Yes goals #142085

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Merged
merged 1 commit into from
Jun 8, 2025
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Don't walk into Certainty::Yes goals #142085

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15 changes: 15 additions & 0 deletions compiler/rustc_hir_typeck/src/fn_ctxt/inspect_obligations.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use rustc_infer::traits::{self, ObligationCause, PredicateObligations};
use rustc_middle::traits::solve::GoalSource;
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use rustc_span::Span;
use rustc_trait_selection::solve::Certainty;
use rustc_trait_selection::solve::inspect::{
InspectConfig, InspectGoal, ProofTreeInferCtxtExt, ProofTreeVisitor,
};
Expand Down Expand Up @@ -117,6 +118,20 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for NestedObligationsForSelfTy<'a, 'tcx> {
}

fn visit_goal(&mut self, inspect_goal: &InspectGoal<'_, 'tcx>) {
// No need to walk into goal subtrees that certainly hold, since they
// wouldn't then be stalled on an infer var.
// FIXME: We also walk into normalizes-to goals since their certainty
// is forced to `Certainty::Yes` since they pass down ambiguous subgoals
// to their parent.
if inspect_goal.result() == Ok(Certainty::Yes)
&& !matches!(
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We currently report nested goals as Certainty::Yes even if they had nested goals... we could/should fix that?

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normalizes-to goals?

in InspectGoal::new, we should also eagerly try to prove the nested goals if the normalizes_to_term_hack is Some 🤔

r=me with a FIXME here saying that normalizes-to nested goals are kinda scuffed or actually fix the impl in this PR

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normalizes-to goals?

Yes, typo.

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Fixed by #142127.

inspect_goal.goal().predicate.kind().skip_binder(),
ty::PredicateKind::NormalizesTo(_)
)
{
return;
}

let tcx = self.fcx.tcx;
let goal = inspect_goal.goal();
if self.fcx.predicate_has_self_ty(goal.predicate, self.self_ty)
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